Characterization of dielectric films for power capacitors by space charge technique

For the last ten years, space charge measurements are used to value the electrical quality of insulating materials. However, the various measurement methods are not adapted to the polymer films employed for the manufacture of power capacitors. The present work is concerned with the development of the new alternative thermal wave method based on the processing of the current response of film samples submitted to alternative thermal stimulations. A thermo-electrical module is used to generate the alternative thermal stimulations. The current response is processed as arising from an equivalent pattern of discrete charged planes parallel to the film faces. Some results obtained with this method on 100 μm thick and 20 μm thick polypropylene films are given. The resolving power of the method and its ability for thinner films are discussed.